Electrochemical cell including electrolyte having insoluble nitrogen-containing material and battery including the cell

ABSTRACT

An electrochemical cell including at least one nitrogen-containing compound is disclosed. The at least one nitrogen-containing compound may form part of or be included in: an anode structure, a cathode structure, an electrolyte and/or a separator of the electrochemical cell. Also disclosed is a battery including the electrochemical cell.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims priority to U.S. patentapplication Ser. No. 14/286,731, filed May 23, 2014, which is acontinuation of and claims priority to U.S. patent application Ser. No.13/227,427 (Now U.S. Pat. No. 8,735,002) filed Sep. 7, 2011 and issuedMay 27, 2014, the disclosures of which are incorporated herein byreference in their entirety for all purposes.

FIELD OF INVENTION

The present invention relates generally to electrochemical cells andelectrochemical cell components. More particularly, the inventionrelates to electrochemical cells including a nitrogen-containingcompound, to components thereof, to batteries including theelectrochemical cells, and to methods of forming and using thebatteries, electrochemical cells and components.

BACKGROUND OF THE INVENTION

There has been considerable interest in recent years in developing highenergy density batteries with lithium containing anodes. Lithium metalis particularly attractive as the anode of electrochemical cells becauseof its extremely light weight and high energy density, compared, forexample, to anodes, such as lithium intercalated carbon anodes, wherethe presence of non-electroactive materials increases weight and volumeof the anode, and thereby reduces the energy density of the cells, andto other electrochemical systems with, for example, nickel or cadmiumanodes. These features are highly desirable for batteries for portableelectronic devices such as cellular phones and laptop computers, as wellas electric vehicles, military, and aerospace applications, where lowweight is important.

Several types of cathode materials for lithium-anode batteries areknown, and include cathode materials comprising sulfur-sulfur bonds,wherein high energy capacity and rechargeability are achieved from theelectrochemical cleavage (via reduction) and reformation (via oxidation)of the sulfur-sulfur bonds. Sulfur-containing cathode materials, havingsulfur-sulfur bonds, for use in electrochemical cells having lithium orsodium anodes, include elemental sulfur, organosulfur, and carbon-sulfurcompositions.

During discharge of batteries that include a lithium anode and asulfur-containing cathode, polysulfides form at the cathode of thebatteries. Certain higher, soluble polysulfides may migrate to the anodeand react with the anode, causing a reduction in battery performance.For example, the battery may exhibit self discharge, due to the presenceof a redox shuttle mechanism, including the higher polysulfides. Thesepolysulfides diffuse through the electrolyte to the anode where they arereduced to lower polysulfides that, in turn, diffuse back through theelectrolyte to the cathode to be oxidized to higher polysulfides. Thisredox shuttle causes a continuous current flow in the cell, resulting ina depletion of the cell's stored capacity.

Accordingly, lithium-anode batteries with reduced self discharge aredesired. In addition, it is generally desirable to have electrochemicalcells with improved performance and properties, such as one or more of:the ability to fully charge, high utilization, high charge-dischargeefficiency, and overcharge protection.

SUMMARY OF THE INVENTION

The present invention generally relates to electrochemical cells andbatteries, and particularly, to: electrochemical cells including alithium anode, a cathode, an electrolyte, and one or more relatively orsubstantially immobile or substantially insoluble nitrogen-containingcompounds, and to batteries including such cells. The substantiallyinsoluble nitrogen-containing compounds are thought to inhibit formationof and/or migration of soluble polysulfides and thereby increase theperformance of the electrochemical cells. While the manner in which thepresent invention is believed to address the drawbacks of prior-artbatteries is discussed in greater detail below, in general, theelectrochemical cells (sometimes referred to herein as “cells”) of theinvention exhibit one or more of reduced self discharge, increasedcharge capacity, increased recharge ratio, increased utilization, andprovide overcharge protection, as compared to similar cells without thenitrogen-containing compounds.

In accordance with various embodiments of the invention, anelectrochemical cell includes an anode containing lithium, a cathode(e.g., containing sulfur), a separator, an electrolyte, and one or moresubstantially immobile and/or substantially insolublenitrogen-containing compounds, which may form part of one or more of theanode, the cathode, the separator, and/or the electrolyte. Duringoperation or cycling of the electrochemical cell, some of thesubstantially insoluble nitrogen-containing compounds may take part inreactions and become depleted; however, other substantially insolublenitrogen-containing compounds may be available (e.g., throughdissolution) and thus the concentration of the substantially insolublenitrogen-containing compounds, in, for example, the electrolyte mayremain relatively constant.

In accordance with various aspects of the embodiments, the substantiallyimmobile and/or insoluble nitrogen-containing compound(s) are confinedor restricted primarily to a particular area of the cell (e.g., thecathode or an anode/electrolyte interface). Restricting the mobility ofthe nitrogen-containing compound(s) may be beneficial, because a desiredresult (e.g., reduced self discharge, while maintaining high chargecapacity and high energy density) may be achieved with relatively smallquantities of the nitrogen-containing compounds, while mitigating anygas production that may otherwise result from the inclusion of similar,more mobile and/or soluble nitrogen-containing compounds within theelectrochemical cell.

In accordance with various aspects of the embodiments of the invention,the one or more nitrogen-containing compounds include an N—O and/or anamine functional group. In accordance with further aspects, the one ormore nitrogen-containing compounds include one or more monomers,oligomers and/or polymers selected from the group consisting of:polyethylene imine, polyphosphazene, polyvinylpyrolidone,polyacrylamide, polyaniline, polyelectrolytes (e.g., having a nitroaliphatic portion as a functional group), and amine groups, such aspolyacrylamide, polyallylaminde and polydiallyldimethylammoniumchloride, polyimides, polybenzimidazole, polyamides, and the like.

In accordance with yet further aspects of embodiments of the invention,the cathode includes a binder comprising the one or morenitrogen-containing compounds.

In accordance with further aspects of embodiments of the invention, thecathode and/or anode includes one or more polymer layers including theone or more nitrogen-containing compounds.

An electrochemical cell according to various exemplary embodiments ofthe invention includes an electrolyte, an anode containing lithium andoptionally, binder(s), coating(s) and/or layer(s), wherein the anodeincludes one or more nitrogen-containing compounds as described above, acathode including sulfur, and a separator. The anode may include abinder including a nitrogen-containing compound and/or a polymer layerincluding a nitrogen-containing compound.

In accordance with yet additional embodiments of the invention, anelectrochemical cell includes an electrolyte (e.g., liquid, solid, orgel) including one or more nitrogen-containing compounds as describedabove, an anode containing lithium, a cathode, and a separator. Theelectrolyte may be a gel or solid electrolyte that is anitrogen-containing compound. Alternatively, the electrolyte is anysuitable electrolyte material that includes one or morenitrogen-containing compounds that are substantially insoluble in theelectrolyte.

In accordance with further embodiments of the invention, a cathode foruse with an electrochemical cell includes a nitrogen-containing compoundas described above. The cathode may include a binder including the oneor more nitrogen-containing compounds, or the cathode may include one ormore polymer layers including the one or more nitrogen-containingcompounds.

In accordance with further embodiments of the invention, an anode foruse in an electrochemical cell includes lithium, one or morenitrogen-containing compounds as described above, and, optionally,binder(s), coating(s) and/or layer(s). In accordance with variousaspects of these embodiments, the one or more nitrogen-containingcompounds include an N—O and/or an amine functional group. The anode mayinclude a binder including a nitrogen-containing compound or the anodemay include a polymer layer including a nitrogen-containing compound.

In accordance with further embodiments of the invention, a separator foruse with an electrochemical cell includes a nitrogen-containing compoundas described above.

In accordance with yet further embodiments of the invention, anelectrolyte for use with an electrochemical cell includes anitrogen-containing compound as described above.

And, in accordance with yet additional embodiments, a battery includesone or more electrochemical cells, wherein each cell includes an anode,a cathode, an electrolyte, and a separator, and wherein one or more ofthe anode, the cathode, the electrolyte, and the separator include anitrogen-containing compound.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

The exemplary embodiments of the present invention will be described inconnection with the appended drawing figures, in which:

FIG. 1 illustrates an electrochemical cell including anitrogen-containing compound in accordance with exemplary embodiments ofthe invention;

FIG. 2 illustrates an anode in accordance with various exemplaryembodiments of the invention; and

FIG. 3 illustrates an anode in accordance with various additionalexemplary embodiments of the invention.

FIG. 4 illustrates a battery in accordance with exemplary embodiments ofthe disclosure.

It will be appreciated that the figures are not necessarily drawn toscale. For example, the dimensions of some of the elements in thefigures may be exaggerated relative to other elements to help to improveunderstanding of illustrated embodiments of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

The description of exemplary embodiments of the present inventionprovided below is merely exemplary and is intended for purposes ofillustration only; the following description is not intended to limitthe scope of the invention disclosed herein.

In accordance with various exemplary embodiments, the present inventionprovides an improved electrochemical cell, and various componentsthereof, suitable for a variety of applications, including, amongothers, automotive, medical device, portable electronics, aviation,military, and aerospace.

Electrochemical cells in accordance with various embodiments of theinvention exhibit one or more of reduced self discharge, increasedcharge capacity, increased recharge ratio, increased utililization, andprovide overcharge protection compared to typical lithium-anode cells.As set forth in more detail below, exemplary electrochemical cellsinclude one or more substantially immobile or substantially insolublenitrogen-containing compounds. Providing one or more nitrogen-containingcompounds may be generally desirable to, for example, increase thecharge capacity of the cell, achieve a high recharge ratio, and reduceself discharge of the cell. However, if the mobility and/or solubilityof the nitrogen-containing compound is not restricted, thenitrogen-containing compound may form undesired levels of nitrogen gasand/or a thickening of the cell during a charge or discharge of thecell, which can result in a corresponding decrease in volumetric energydensity of the cell. Accordingly, electrochemical cells and componentsthereof, in accordance with various embodiments of the invention,include substantially immobile and/or insoluble nitrogen-containingcompounds.

FIG. 1 illustrates an electrochemical cell 100, including anitrogen-containing compound, in accordance with various exemplaryembodiments of the invention. Cell 100 includes a cathode 102(optionally including a cathode coating or layer 110), an anode 104, anelectrolyte 106, a separator 108, and optionally includes currentcollectors 112, 114.

Cathode 102 includes an active material. Suitable cathode activematerials for use in cathode 102 and electrochemical cells describedherein include, but are not limited to, electroactive transition metalchalcogenides, electroactive conductive polymers, and electroactivesulfur-containing materials, and combinations thereof. In accordancewith various exemplary embodiments, the cathode active layer comprisesan electroactive conductive polymer. Examples of suitable electroactiveconductive polymers include, but are not limited to, electroactive andelectronically conductive polymers selected from the group consisting ofpolypyrroles, polyanilines, polyphenylenes, polythiophenes, andpolyacetylenes. As set forth in more detail below, in accordance withvarious embodiments of the invention, cathode 102 additionally includesone or more nitrogen-containing materials.

In accordance with aspects of these embodiments, cathode 102 includesone or more electroactive sulfur materials and, optionally, one or morenitrogen-containing materials. “Electroactive sulfur-containingmaterials,” as used herein, relates to cathode active materials whichcomprise the element sulfur in any form, wherein the electrochemicalactivity involves the breaking or forming of sulfur-sulfur covalentbonds. Suitable electroactive sulfur-containing materials include, butare not limited to, elemental sulfur and organic materials comprisingsulfur atoms and carbon atoms, which may or may not be polymeric.Suitable organic materials include those further comprising heteroatoms,conductive polymer segments, composites, and conductive polymers. Inaccordance with additional aspects, the electroactive sulfur-containingmaterials include elemental sulfur. In accordance with other examples,the electroactive sulfur-containing material comprises a mixture ofelemental sulfur and a sulfur-containing polymer.

“Nitrogen-containing materials,” in accordance with various exemplaryembodiments of the invention, include compounds including an N—O (e.g.,nitro) and/or an amine functional group. In accordance with variousexemplary aspects of these embodiments, the one or morenitrogen-containing compounds include one or more monomers, oligomersand/or polymers selected from the group consisting of: polyethyleneimine, polyphosphazene, polyvinylpyrolidone, polyacrylamide,polyaniline, polyelectrolytes (e.g., having a nitro aliphatic portion asfunctional group), and amine groups, such as polyacrylamide,polyallylaminde and polydiallyldimethylammonium chloride, polyimides,polybenzimidazole, polyamides, and the like. The polyelectrolytes foruse in accordance with various exemplary embodiments may be synthesizedby, for example, direct nitration reactions with nitric acid andmonomers, oligomers, and/or polymers having an aromatic group, suchthat, for example, nitro functional groups are incorporated into themonomers, oligomers, and/or polymers. Exemplary monomers, oligomers,and/or polymers suitable for the exemplary polyelectrolytes includepolystyrenes, polyarylenes, such as polysulfones, polyether keytones,polyphenylenes, and the like.

Additionally or alternatively, the nitrogen-containing material may be asubstantially insoluble compound (e.g., insoluble in the electrolyte).As used herein, “substantially insoluble” means less than 1% or lessthan 0.5% solubility of the compound in the electrolyte; all percentsset forth herein are weight or mass percent, unless otherwise noted.Substantially insoluble compounds can be formed by, for example,attaching an insoluble cation, monomer, oligomer, or polymer, such aspolystyrene or cellulose to a nitrogen-containing compound to formpolynitrostyrene or nitrocellulose. One such substantially insolublecompound is octyl nitrate. Additionally or alternatively, compounds,such as salts of K, Mg, Ca, Sr, Al, aromatic hydrocarbons, or ethers asbutyl ether may be added to the electrolyte to reduce the solubility ofnitrogen-containing compounds, such as inorganic nitrate, organicnitrates, inorganic nitrites, organic nitrites, organic nitro compounds,and the like, such that otherwise soluble or mobile nitrogen-containingmaterials become substantially insoluble and/or substantially immobilein the electrolyte.

Another approach to reducing the mobility and/or solubility ofnitrogen-containing materials, to form substantially insolublenitrogen-containing compounds, includes attaching an N—O (e.g., nitro)and/or amine functional group to a long carbon chain, having, forexample, about 8 to about 25 carbon atoms, to form micellar-typestructures, with the active groups (e.g., nitrates) facing theelectrolyte solution.

Cathode 102 may additionally include an electroactive transition metalchalcogenide, and, optionally, binders, electrolytes, and conductiveadditives. In accordance with various exemplary embodiments of theinvention, the transition metal chalcogenide, binders, electrolytes,and/or conductive additives are functionalized (e.g., with a nitro oramine functional group) and are a nitrogen-containing compound. Theelectroactive material may be encapsulated or impregnated by thetransition metal chalcogenide. In another embodiment, a coating of theelectroactive sulfur-containing cathode material is encapsulated orimpregnated by a thin coherent film coating of the cation transporting,anionic reduction product transport-retarding, transition metalchalcogenide composition. In yet another embodiment, a cathode includesparticulate electroactive sulfur-containing cathode materialsindividually coated with an encapsulating layer of the cationtransporting, anionic reduction product transport-retarding, transitionmetal chalcogenide composition. Other configurations are also possible.

In accordance with certain embodiments, the composite cathode is aparticulate, porous electroactive transition metal chalcogenidecomposition, optionally containing nonelectroactive metal oxides, suchas silica, alumina, and silicates, that is further impregnated with asoluble electroactive sulfur-containing cathode material. This may bebeneficial in increasing the energy density and capacity compared withcathodes including electroactive sulfur-containing cathode material(e.g., electroactive organosulfur and carbon-sulfur cathode materials)only. In accordance with various aspects of these embodiments, thetransition metal chalcogenide and/or the metal oxide may befunctionalized with a nitrogen-containing group to be anitrogen-containing compound.

Cathode 102 may further comprise one or more conductive fillers toprovide enhanced electronic conductivity. Conductive fillers canincrease the electrically-conductive properties of a material and mayinclude, for example, conductive carbons such as carbon black (e.g.,Vulcan XC72R carbon black, Printex XE2, or Akzo Nobel Ketjen EC-600 JD),graphite fibers, graphite fibrils, graphite powder (e.g., Fluka #50870),activated carbon fibers, carbon fabrics, non-activated carbonnanofibers. Other non-limiting examples of conductive fillers includemetal coated glass particles, metal particles, metal fibers,nanoparticles, nanotubes, nanowires, metal flakes, metal powders, metalfibers, and metal mesh. In some embodiments, a conductive filler mayinclude a conductive polymer. Examples of suitable electroactiveconductive polymers include, but are not limited to, electroactive andelectronically conductive polymers selected from the group consisting ofpolypyrroles, polyanilines, polyphenylenes, polythiophenes, andpolyacetylenes. Other conductive materials known to those of ordinaryskill in the art can also be used as conductive fillers. The amount ofconductive filler, if present, may be present in the range of 2 to 30%by weight of the cathode active layer. In accordance with variousexemplary embodiments of the invention, the filler is functionalizedwith a nitrogen group, such as an N—O or amine group. Cathode 102 mayalso further comprise other additives including, but not limited to,metal oxides, aluminas, silicas, and transition metal chalcogenides,which may additionally or alternatively be functionalized with anitrogen-containing group, such as an amine or N—O group.

Cathode 102 may also include a binder. In some embodiments, the bindermaterial may be a polymeric material. Examples of polymer bindermaterials include, but are not limited to, polyvinylidene fluoride(PVDF)-based polymers, such as poly(vinylidene fluoride) (PVDF), PVF2and its co- and terpolymers with hexafluoroethylene,tetrafluoroethylene, chlorotrifluoroethylene, poly(vinyl fluoride),polytetrafluoroethylenes (PTFE), ethylene-tetrafluoroethylene copolymers(ETFE), polybutadiene, cyanoethyl cellulose, carboxymethyl cellulose andits blends with styrene-butadiene rubber, polyacrylonitrile,ethylene-propylene-diene (EPDM) rubbers, ethylene propylene dieneterpolymers, styrene-butadiene rubbers (SBR), polyimides orethylene-vinyl acetate copolymers. In some cases, the binder materialmay be substantially soluble in aqueous fluid carriers and may include,but is not limited to, cellulose derivatives, typically methylcellulose(MC), carboxy methylcellulose (CMC) and hydroxypropyl methylcellulose(HPMC), polyvinyl alcohol (PVA), polyacrylic acid salts, polyacryl amide(PA), polyvinyl pyrrolidone (PVP) and polyethylene oxides (PEO). In oneset of embodiments, the binder material ispoly(ethylene-co-propylene-co-5-methylene-2-norbornene) (EPMN), whichmay be chemically neutral (e.g., inert) towards cell components,including polysulfides. UV curable acrylates, UV curable methacrylates,and heat curable divinyl ethers can also be used. The amount of binder,if present, may be present in the range of 2 to 30% by weight of thecathode active layer. In accordance with various exemplary embodimentsof the invention, the binder is functionalized with a nitrogen group,such as an N—O (e.g., nitro) or amine group.

In some embodiments, a cathode comprises a conductive porous supportstructure and a plurality of particles comprising sulfur (e.g., as anactive species) substantially contained within the pores of the supportstructure.

A porous support structure can comprise any suitable form. In someinstances, the porous support structure can comprise a porousagglomeration of discrete particles, within which the particles can beporous or non-porous. For example, the porous support structure might beformed by mixing porous or non-porous particles with a binder to form aporous agglomeration. Electrode active material might be positionedwithin the interstices between the particles and/or the pores within theparticles (in cases where porous particles are employed) to form theinventive electrodes described herein.

In some embodiments, the porous support structure can be a “porouscontinuous” structure. A porous continuous structure, as used herein,refers to a continuous solid structure that contains pores within it,with relatively continuous surfaces between regions of the solid thatdefine the pores. Examples of porous continuous structures include, forexample, material that includes pores within its volume (e.g., a porouscarbon particle, a metal foam, etc.). One of ordinary skill in the artwill be capable of differentiating between a porous continuous structureand, for example, a structure that is not a porous continuous structure,but which is a porous agglomeration of discrete articles (where theinterstices and/or other voids between the discrete particles would beconsidered pores) by, for example, comparing SEM images of the twostructures. In accordance with various embodiments of the invention, theporous support includes functional nitrogen groups, such as N—O and/oramine groups and is a nitrogen-containing compound.

The porous support structure may be of any suitable shape or size. Forexample, the support structure can be a porous continuous particle withany suitable maximum cross-sectional dimension (e.g., less than about 10mm, less than about 1 mm, less than about 500 microns, etc.). In somecases, the porous support structure (porous continuous or otherwise) canhave a relatively large maximum cross-sectional dimension (e.g., atleast about 500 microns, at least about 1 mm, at least about 10 mm, atleast about 10 cm, between about 1 mm and about 50 cm, between about 10mm and about 50 cm, or between about 10 mm and about 10 cm). In someembodiments, the maximum cross-sectional dimension of a porous supportstructure within an electrode can be at least about 50%, at least about75%, at least about 90%, at least about 95%, at least about 98%, or atleast about 99% of the maximum cross-sectional dimension of theelectrode formed using the porous continuous structure.

By way of more particular examples, cathode 102 may include greater thanabout 40%, or about 45% to about 95%, or about 55% to about 75%electroactive sulfur-containing materials, and up to about 20%, or about0.5% to about 4%, or about 1% to about 2% nitrogen-containing materials,for example, materials having functional N—O or amine groups, up toabout 40%, or about 2% to about 30%, or about 10 to about 20% filler,and up to about 40%, or about 2% to about 30%, or about 10% to about 20%binder.

As previously stated, the nitrogen-containing materials may be afunctionalized polymer, transition metal chalcogenide, metal oxide,filler, and/or binder. Additionally or alternatively, thenitrogen-containing material may be in the form of cathode coating 110,formed of, for example, one or more monomers, oligomers and/or polymersselected from one or more of the group consisting of: polyethyleneimine, polyphosphazene, polyvinylpyrolidone, polyacrylamide,polyaniline, polyelectrolytes (e.g., having a nitro aliphatic portion asa functional group), and amine groups, such as polyacrylamide,polyallylaminde and polydiallyldimethylammonium chloride, polyimides,polybenzimidazole, polyamides, and the like.

Anode 104 may be of any structure suitable for use in a givenelectrochemical cell with a given cathode. Suitable active materials,comprising lithium, for anode 104 include, but are not limited to,lithium metal, such as lithium foil and lithium deposited onto asubstrate, such as a plastic film, and lithium alloys, such aslithium-aluminum alloys and lithium-tin alloys.

In certain embodiments, the thickness of the anode may vary from, e.g.,about 2 to 200 microns. For instance, the anode may have a thickness ofless than 200 microns, less than 100 microns, less than 50 microns, lessthan 25 microns, less than 10 microns, or less than 5 microns. Thechoice of the thickness may depend on cell design parameters such as theexcess amount of lithium desired, cycle life, and the thickness of thecathode electrode. In one embodiment, the thickness of the anode activelayer is in the range of about 2 to 100 microns (e.g., about 5 to 50microns, about 5 to 25 microns, or about 10 to 25 microns).

The layers of an anode may be deposited by any of a variety of methodsgenerally known in the art, such as physical or chemical vapordeposition methods, extrusion, or electroplating. Examples of suitablephysical or chemical vapor deposition methods include, but are notlimited to, thermal evaporation (including, but not limited to,resistive, inductive, radiation, and electron beam heating), sputtering(including, but not limited to, diode, DC magnetron, RF, RF magnetron,pulsed, dual magnetron, AC, MF, and reactive), chemical vapordeposition, plasma enhanced chemical vapor deposition, laser enhancedchemical vapor deposition, ion plating, cathodic arc, jet vapordeposition, and laser ablation.

Deposition of the layers may be carried out in a vacuum or inertatmosphere to minimize side reactions in the deposited layers whichcould introduce impurities into the layers or which may affect thedesired morphology of the layers. In some embodiments, anode activelayers and the layers of multi-layered structures are deposited in acontinuous fashion in a multistage deposition apparatus.

Alternatively, where the anode comprises a lithium foil, or a lithiumfoil and a substrate, these can be laminated together by a laminationprocess as known in the art, to form an anode layer.

FIG. 2 illustrates anode 104, including a base electrode material layer202, (e.g., comprising an electroactive material such as lithium) and amulti-layered structure 204, in accordance with various exemplaryembodiments of the invention. In some cases herein, the anode isreferred to as an “anode based material,” “anode active material,” orthe like, and the anode along with any protective structures arereferred to collectively as the “anode.” All such descriptions are to beunderstood to form part of the invention. In this particular embodiment,multi-layered structure 204 includes a single-ion conductive layer or asingle-ion conductive layer 206, a polymeric layer 208 positionedbetween the base electrode material and the single-ion conductivematerial, and a separation layer 210 (e.g., a layer resulting fromplasma treatment of the electrode) positioned between the electrode andthe polymeric layer. As discussed in more detail below, variouscomponents of anode 104 may be functionalized with a nitrogen group, inaccordance with various exemplary embodiments of the invention.

Multi-layered structure 204 can allow passage of lithium ions and mayimpede the passage of other components that may otherwise damage theanode. Multilayered structure 204 can reduce the number of defects andthereby force at least some of the surface of the base electrodematerial to participate in current conduction, impede high currentdensity-induced surface damage, and/or act as an effective barrier toprotect the anode from certain species (e.g., electrolyte and/orpolysulfides), as discussed in greater detail below.

In some embodiments, single-ion conductive layer 206 material isnon-polymeric. In certain embodiments, the single-ion conductivematerial layer is defined in part or in whole by a metal layer that ishighly conductive toward lithium and minimally conductive towardelectrons. In other words, the single-ion conductive material may be oneselected to allow lithium ions, but to impede electrons or other ions,from passing across the layer. The metal layer may comprise a metalalloy layer, e.g., a lithiated metal layer. The lithium content of themetal alloy layer may vary from about 0.5% by weight to about 20% byweight, depending, for example, on the specific choice of metal, thedesired lithium ion conductivity, and the desired flexibility of themetal alloy layer. Suitable metals for use in the single-ion conductivematerial include, but are not limited to, Al, Zn, Mg, Ag, Pb, Cd, Bi,Ga, In, Ge, Sb, As, and Sn. Sometimes, a combination of metals, such asthe ones listed above, may be used in a single-ion conductive material.

In other embodiments, single-ion conductive layer 206 material mayinclude a ceramic layer, for example, a single ion conducting glassconductive to lithium ions. Suitable glasses include, but are notlimited to, those that may be characterized as containing a “modifier”portion and a “network” portion, as known in the art. The modifier mayinclude a metal oxide of the metal ion conductive in the glass. Thenetwork portion may include a metal chalcogenide such as, for example, ametal oxide or sulfide. Single-ion conductive layers may include glassylayers comprising a glassy material selected from the group consistingof lithium nitrides, lithium silicates, lithium borates, lithiumaluminates, lithium phosphates, lithium phosphorus oxynitrides, lithiumsilicosulfides, lithium germanosulfides, lithium oxides (e.g., Li₂O,LiO, LiO₂, LiRO₂, where R is a rare earth metal), lithium lanthanumoxides, lithium titanium oxides, lithium borosulfides, lithiumaluminosulfides, and lithium phosphosulfides, and combinations thereof.In one embodiment, the single-ion conductive layer comprises a lithiumphosphorus oxynitride in the form of an electrolyte.

A thickness of single-ion conductive material layer 206 (e.g., within amultilayered structure) may vary over a range from about 1 nm to about10 microns. For instance, the thickness of the single-ion conductivematerial layer may be between 1-10 nm thick, between 10-100 nm thick,between 100-1000 nm thick, between 1-5 microns thick, or between 5-10microns thick. The thickness of a single-ion conductive material layermay be no greater than, e.g., 10 microns thick, no greater than 5microns thick, no greater than 1000 nm thick, no greater than 500 nmthick, no greater than 250 nm thick, no greater than 100 nm thick, nogreater than 50 nm thick, no greater than 25 nm thick, or no greaterthan 10 nm thick. In some cases, the single-ion conductive layer has thesame thickness as a polymer layer in a multi-layered structure.

Single-ion conductive layer 206 may be deposited by any suitable methodsuch as sputtering, electron beam evaporation, vacuum thermalevaporation, laser ablation, chemical vapor deposition (CVD), thermalevaporation, plasma enhanced chemical vacuum deposition (PECVD), laserenhanced chemical vapor deposition, and jet vapor deposition. Thetechnique used may depend on any factor related to the layer beingdeposited, such as the nature of the material being deposited or thethickness of the layer.

In some embodiments, suitable polymer layers for use in a multi-layeredstructure (e.g., such as polymer layer 208) include polymers that arehighly conductive towards lithium and minimally conductive towardselectrons. Examples of such polymers include ionically conductivepolymers, sulfonated polymers, and hydrocarbon polymers. The selectionof the polymer will be dependent upon a number of factors including theproperties of electrolyte and cathode used in the cell. Suitableionically conductive polymers include, e.g., ionically conductivepolymers known to be useful in solid polymer electrolytes and gelpolymer electrolytes for lithium electrochemical cells, such as, forexample, polyethylene oxides.

Suitable sulfonated polymers may include, e.g., sulfonated siloxanepolymers, sulfonated polystyrene-ethylene-butylene polymers, andsulfonated polystyrene polymers. Suitable hydrocarbon polymers mayinclude, e.g., ethylene-propylene polymers, polystyrene and/or polymers.

Polymer layers 208 of a multi-layered structure 204 can also includecrosslinked polymer materials formed from the polymerization of monomerssuch as alkyl acrylates, glycol acrylates, polyglycol acrylates,polyglycol vinyl ethers, and/or polyglycol divinyl ethers. For example,one such crosslinked polymer material is polydivinyl poly(ethyleneglycol). The crosslinked polymer materials may further comprise salts,for example, lithium salts, to enhance ionic conductivity. In oneembodiment, the polymer layer of the multi-layered structure comprises acrosslinked polymer.

Other classes of polymers that may be suitable for use in a polymerlayer include, but are not limited to, polyamines (e.g., poly(ethyleneimine) and polypropylene imine (PPI)); polyamides (e.g., polyamide(Nylon), poly(e-caprolactam) (Nylon 6), poly(hexamethylene adipamide)(Nylon 66)), polyimides (e.g., polyimide, polynitrile, andpoly(pyromellitimide-1,4-diphenyl ether) (Kapton)); vinyl polymers(e.g., polyacrylamide, poly(2-vinyl pyridine), poly(N-vinylpyrrolidone),poly(methylcyanoacrylate), poly(ethylcyanoacrylate),poly(butylcyanoacrylate), poly(isobutylcyanoacrylate), poly(vinylacetate), poly (vinyl alcohol), poly(vinyl chloride), poly(vinylfluoride), poly(2-vinyl pyridine), vinyl polymer, polychlorotrifluoroethylene, and poly(isohexylcynaoacrylate)); polyacetals; polyolefins(e.g., poly(butenel), poly(n-pentene-2), polypropylene,polytetrafluoroethylene); polyesters (e.g., polycarbonate, polybutyleneterephthalate, polyhydroxybutyrate); polyethers (poly(ethylene oxide)(PEO), poly(propylene oxide) (PPO), poly(tetramethylene oxide) (PTMO));vinylidene polymers (e.g., polyisobutylene, poly(methyl styrene),poly(methylmethacrylate) (PMMA), poly(vinylidene chloride), andpoly(vinylidene fluoride)); polyaramides (e.g., poly(imino-1,3-phenyleneiminoisophthaloyl) and poly(imino-1,4-phenylene iminoterephthaloyl));polyheteroaromatic compounds (e.g., polybenzimidazole (PBI),polybenzobisoxazole (PBO) and polybenzobisthiazole (PBT));polyheterocyclic compounds (e.g., polypyrrole); polyurethanes; phenolicpolymers (e.g., phenol-formaldehyde); polyalkynes (e.g., polyacetylene);polydienes (e.g., 1,2-polybutadiene, cis or trans-1,4-polybutadiene);polysiloxanes (e.g., poly(dimethylsiloxane) (PDMS),poly(diethylsiloxane) (PDES), polydiphenylsiloxane (PDPS), andpolymethylphenylsiloxane (PMPS)); and inorganic polymers (e.g.,polyphosphazene, polyphosphonate, polysilanes, polysilazanes).

The polymer materials listed above and described herein may furthercomprise salts, for example, lithium salts (e.g., LiSCN, LiBr, LiI,LiClO₄, LiAsF₆, LiSO₃CF₃, LiSO₃CH₃, LiBF₄, LiB(Ph)₄, LiPF₆,LiC(SO₂CF₃)₃, and LiN(SO₂CF₃)₂), to enhance ionic conductivity.

The thickness of polymer layer 208 may vary, e.g., over a range fromabout 0.1 microns to about 100 microns. The thickness of the polymerlayer may depend on, for example, whether it is positioned adjacent theanode or cathode, whether a separator is also present in the battery,and/or the number of polymer layers in the battery. For instance, thethickness of the polymer layer may be between 0.1-1 microns thick,between 1-5 microns thick, between 5-10 microns thick, between 10-30microns thick, or between 30-50 microns thick, between 50-70 micronsthick, or between 50-100 microns thick. In some embodiments, thethickness of a polymer layer may be no greater than, e.g., 50 micronsthick, no greater than 25 microns thick, no greater than 10 micronsthick, no greater than 5 microns thick, no greater than 2.5 micronsthick, no greater than 1 micron thick, no greater than 0.5 micronsthick, or no greater than 0.1 microns thick.

A polymer layer may be deposited by method such as electron beamevaporation, vacuum thermal evaporation, laser ablation, chemical vapordeposition, thermal evaporation, plasma assisted chemical vacuumdeposition, laser enhanced chemical vapor deposition, jet vapordeposition, and extrusion. The polymer layer may also be deposited byspin-coating techniques. The technique used for depositing polymerlayers may depend on any suitable variable, such as the type of materialbeing deposited, or the thickness of the layer. In accordance withvarious embodiments of the invention, the polymer layer isfunctionalized with a nitrogen group as described herein.

As noted in the description with respect to anode 104, illustrated inFIG. 2, in one particular embodiment, multi-layered structure 204,separating base electrode material layer 202 from electrolyte 106,includes polymer layer 208 adjacent either base electrode material layer202 or separation layer 210. In other arrangements, a polymer layer neednot be the first layer adjacent the base electrode material layer orseparation layer. Various arrangements of layers, including variousmulti-layered structures, are described below, in which the first layeradjacent the base electrode material layer may or may not be the polymerlayer. It is to be understood that in all arrangements where anyparticular arrangement of layers is shown, alternate ordering of layersis within the scope of the invention. Notwithstanding this, one aspectof the invention includes the particular advantages realized by anon-brittle polymer immediately adjacent either the base electrodematerial layer or separation layer.

A multi-layered structure can include various numbers ofpolymer/single-ion conductive pairs as needed. Generally, amulti-layered structure can have n polymer/single-ion conductive pairs,where n can be determined based on a particular performance criteria fora cell. For example, n can be an integer equal to or greater than 1, orequal to or greater than 2, 3, 4, 5, 6, 7, 10, 15, 20, 40, 60, 100, or1000, etc.

In other embodiments, a multi-layered structure may include a greaternumber of polymer layers than single-ion conductive layers, or a greaternumber of single-ion conductive layers than polymer layers. For example,a multi-layered structure may include n polymer layers and n+1single-ion conductive layers, or n single-ion conductive layers and n+1polymer layers, where n is greater than or equal to 2. For example, nmay equal 2, 3, 4, 5, 6, or 7, or higher. However, as described above,it is immediately adjacent at least one polymer layer and, in at least50%, 70%, 90%, or 95% of the ion-conductive layers, such layers areimmediately adjacent a polymer layer on either side.

Another embodiment includes an embedded layer (e.g., of a protectivelayer such as a single-ion conductive material layer) positioned betweentwo layers of base electrode materials. This is referred to as a“lamanode” structure. FIG. 3 illustrates an exemplary anode 104including a first layer of a base electrode material layer 202 (e.g.,lithium, also referred to as a Li reservoir), embedded layer 302, and asecond layer 304 comprising the base electrode material (a working Lilayer). As illustrated in FIG. 3, second layer 304 is positioned betweenbase electrode material layer 202 and electrolyte 106. Second layer 304may be either in direct contact with the electrolyte, or in indirectcontact with the electrolyte through some form of a surface layer (e.g.,an electrode stabilization or multi-layered structure such as onedescribed herein). The function of the bi-layer anode structure, witheach base electrode material layer separated by an embedded layer 302,will become clearer from the description below. It is noted thatalthough embedded layer 302 is illustrated and described as “embedded”in this description, it is noted that the layer need not be partially orfully embedded. In many or most cases, embedded layer 302 is asubstantially thin, two-sided structure coated on each side by baseelectrode material, but not covered by base electrode material at itsedges.

In general, in operation of the arrangement shown in FIG. 3, some or allof second layer 304 of the anode is “lost” from the anode upon discharge(when it is converted to lithium ion which moves into the electrolyte).Upon charge, when lithium ion is plated as lithium metal onto the anode,it is plated as second layer 304 (or at least some portion of secondlayer 304) above embedded layer 302. Those of ordinary skill in the artare aware that in electrochemical cells such as those described herein,there is a small amount of overall lithium loss on each charge/dischargecycle of the cell. In the arrangement illustrated in FIG. 3, thethickness of second layer 304 (or the mass of second layer 304) can beselected such that most or all of second layer 304 is lost upon fulldischarge of the cell (full “satisfaction” of the cathode; the point atwhich the cathode can no longer participate in a charging process due tolimitations that would be understood by those of ordinary skill in theart).

In certain embodiments, embedded layer 302 is selected to be one that isconductive to lithium ions. The embedded layer can shield the bottom Lilayer from damage as the high Li+ flux of the first cycle damages thetop Li layer surface. Accordingly, once all of second layer 304 isconsumed in a particular discharge cycle, further discharge results inoxidation of lithium from base electrode material layer 202, passage oflithium ion through embedded layer 302, and release of lithium ion intothe electrolyte. Of course, second layer 304 need not be of a particularmass such that all or nearly all of it is consumed on first discharge.It may take several discharge/charge cycles, and inherent small amountsof lithium loss through each cycle, to result in the need to drawlithium from base electrode material layer 202 through embedded layer302 and into the electrolyte.

In some embodiments, embedded layer 302 may have a thickness between0.01-1 microns, and may depend on, e.g., the type of material used toform the embedded layer and/or the method of depositing the material.For example, the thickness of the embedded layer may be between 0.01-0.1microns, between 0.1-0.5 microns, or between 0.5-1 micron. In otherembodiments, thicker embedded layers are included. For example, theembedded layer can have a thickness between 1-10 microns, between 10-50microns, or between 50-100 microns.

In some cases, the embedded material can be formed of a polymer, e.g.,including ones listed above that are lithium ion conductive. The polymerfilm can be deposited using techniques such as vacuum based PML, VMT orPECVD techniques. In other cases, an embedded layer can comprise a metalor semiconductor material. Metals and semi-conductors can be, forexample, sputtered.

By way of particular examples, anode 104 includes lithium and at leastone layer of a nitrogen-containing material. The nitrogen-containingmaterial may be a functionalized surface having, for example, and amineor nitro group or include one or more monomers, oligomers and/orpolymers selected from the group consisting of: polyethylene imine,polyphosphazene, polyvinylpyrolidone, polyacrylamide, polyaniline,polyelectrolytes (e.g., having a nitro aliphatic portion as a functionalgroup), and amine groups, such as polyacrylamide, polyallylaminde andpolydiallyldimethylammonium chloride, polyimides, polybenzimidazole,polyamides, and the like. A percent of nitrogen-containing compound anpart of the anode may range from up to about 20%, about 0.5% to about5%, or about 1 to about 2%.

Electrolyte 106 can function as a medium for the storage and transportof ions, and in the special case of solid electrolytes and gelelectrolytes, these materials may additionally function as a separator(e.g., separator 108) between anode 104 and cathode 102. Any suitableliquid, solid, or gel material capable of storing and transporting ionsbetween the anode and the cathode may be used. Electrolyte 106 may beelectronically non-conductive to prevent short circuiting between anode104 and cathode 102.

The electrolyte can comprise one or more ionic electrolyte salts toprovide ionic conductivity and one or more liquid electrolyte solvents,gel polymer materials, or polymer materials.

Suitable non-aqueous electrolytes may include organic electrolytescomprising one or more materials selected from the group consisting ofliquid electrolytes, gel polymer electrolytes, and solid polymerelectrolytes.

Examples of useful non-aqueous liquid electrolyte solvents include, butare not limited to, non-aqueous organic solvents, such as, for example,N-methyl acetamide, acetonitrile, acetals, ketals, esters, carbonates,sulfones, sulfites, sulfolanes, aliphatic ethers, acyclic ethers, cyclicethers, glymes, polyethers, phosphate esters, siloxanes, dioxolanes,N-alkylpyrrolidones, substituted forms of the foregoing, and blendsthereof. Examples of acyclic ethers that may be used include, but arenot limited to, diethyl ether, dipropyl ether, dibutyl ether,dimethoxymethane, trimethoxymethane, dimethoxyethane, diethoxyethane,1,2-dimethoxypropane, and 1,3-dimethoxypropane. Examples of cyclicethers that may be used include, but are not limited to,tetrahydrofuran, tetrahydropyran, 2-methyltetrahydrofuran, 1,4-dioxane,1,3-dioxolane, and trioxane. Examples of polyethers that may be usedinclude, but are not limited to, diethylene glycol dimethyl ether(diglyme), triethylene glycol dimethyl ether (triglyme), tetraethyleneglycol dimethyl ether (tetraglyme), higher glymes, ethylene glycoldivinylether, diethylene glycol divinylether, triethylene glycoldivinylether, dipropylene glycol dimethyl ether, and butylene glycolethers. Examples of sulfones that may be used include, but are notlimited to, sulfolane, 3-methyl sulfolane, and 3-sulfolene. Fluorinatedderivatives of the foregoing are also useful as liquid electrolytesolvents. Mixtures of the solvents described herein can also be used.

In some embodiments, specific liquid electrolyte solvents that may befavorable towards anode 104 include, but are not limited to,1,1-dimethoxyethane (1,1-DME), 1,1diethoxyethane, 1,2-diethoxyethane,diethoxymethane, dibutyl ether, anisole or methoxybenzene, veratrole or1,2-dimethoxybenzene, 1,3-dimethoxybenzene, tbutoxyethoxyethane,2,5-dimethoxytetrahydrofurane, cyclopentanone ethylene ketal, andcombinations thereof. Specific liquid electrolyte solvents that may befavorable towards the cathode 102 (e.g., have relatively highpolysulfide solubility, and/or can enable high rate capability and/orhigh sulfur utilization) include, but are not limited to,dimethoxyethane (DME, 1,2-dimethoxyethane) or glyme, diglyme, triglyme,tetraglyme, polyglymes, sulfolane, 1,3-dioxolane (DOL), tetrahydrofurane(THF), acetonirile, and combinations thereof.

Specific mixtures of solvents include, but are not limited to,1,3-dioxolane and dimethoxyethane, 1,3-dioxolane and diethyleneglycoldimethyl ether, 1,3-dioxolane and triethyleneglycol dimethyl ether, and1,3-dioxolane and sulfolane. The weight ratio of the two solvents in themixtures may vary from about 5 to 95 to 95 to 5. In some embodiments, asolvent mixture comprises dioxolanes (e.g., greater than 40% by weightof dioxolanes).

Liquid electrolyte solvents can also be useful as plasticizers for gelpolymer electrolytes. Examples of useful gel polymer electrolytesinclude, but are not limited to, those comprising one or more polymersselected from the group consisting of polyethylene oxides, polypropyleneoxides, polyacrylonitriles, polysiloxanes, polyimides, polyphosphazenes,polyethers, sulfonated polyimides, perfluorinated membranes (NAFIONresins), polydivinyl polyethylene glycols, polyethylene glycoldiacrylates, polyethylene glycol dimethacrylates, derivatives of theforegoing, copolymers of the foregoing, crosslinked and networkstructures of the foregoing, and blends of the foregoing, andoptionally, one or more plasticizers.

Examples of useful solid polymer electrolytes include, but are notlimited to, those comprising one or more polymers selected from thegroup consisting of polyethers, polyethylene oxides, polypropyleneoxides, polyimides, polyphosphazenes, polyacrylonitriles, polysiloxanes,derivatives of the foregoing, copolymers of the foregoing, crosslinkedand network structures of the foregoing, and blends of the foregoing.

In addition to electrolyte solvents, gelling agents, and polymers asknown in the art for forming electrolytes, the electrolyte may furthercomprise one or more ionic electrolyte salts, also as known in the art,to increase the ionic conductivity.

Examples of ionic electrolyte salts for use in the electrolytesdescribed herein include, but are not limited to, LiSCN, LiBr, LiI,LiClO₄, LiAsF₆, LiSO₃CF₃, LiSO₃CH₃, LiBF₄, LiB(Ph)₄, LiPF₆,LiC(SO₂CF₃)₃, and LiN(SO₂CF₃)₂. Other electrolyte salts that may beuseful include lithium polysulfides (Li₂Sx), and lithium salts oforganic ionic polysulfides (LiS_(x)R)_(n), where x is an integer from 1to 20, n is an integer from 1 to 3, and R is an organic group, and thelike range of concentrations of the ionic lithium salts in the solventmay be used such as from about 0.2 m to about 2.0 m (m is moles/kg ofsolvent). In some embodiments, a concentration in the range betweenabout 0.5 m to about 1.5 m is used. The addition of ionic lithium saltsto the solvent is optional in that upon discharge of Li/S cells thelithium sulfides or polysulfides formed typically provide ionicconductivity to the electrolyte, which may make the addition of ioniclithium salts unnecessary. Furthermore, if an ionic N—O additive such asan inorganic nitrate, organic nitrate, inorganic nitrite, orpolyelectrolyte is used, it may provide ionic conductivity to theelectrolyte in which case no additional ionic lithium electrolyte saltsmay be needed.

As described herein, additives that may reduce or prevent formation ofimpurities and/or depletion of electrochemically active materials,including electrodes and electrolyte materials, during charge/dischargeof the electrochemical cell, may be incorporated into electrochemicalcells described herein.

In some cases, an additive such as an organometallic compound may beincorporated into the electrolyte and may reduce or prevent interactionbetween at least two components or species of the cell to increase theefficiency and/or lifetime of the cell. Typically, electrochemical cells(e.g., rechargeable batteries) undergo a charge/discharge cycleinvolving deposition of metal (e.g., lithium metal) on the surface ofthe anode (e.g., a base electrode material) upon charging and reactionof the metal on the anode surface to form metal ions, upon discharging.The metal ions may diffuse from the anode surface into an electrolytematerial connecting the cathode with the anode. The efficiency anduniformity of such processes may affect cell performance. For example,lithium metal may interact with one or more species of the electrolyteto substantially irreversibly form lithium-containing impurities,resulting in undesired depletion of one or more active components of thecell (e.g., lithium, electrolyte solvents). The incorporation of certainadditives within the electrolyte of the cell have been found, inaccordance with certain embodiments described herein, to reduce suchinteractions and to improve the cycling lifetime and/or performance ofthe cell.

In some embodiments, the additive may be any suitable species, or saltthereof, capable of reducing or preventing the depletion of activematerials (e.g., electrodes, electrolyte) within a cell, for example, byreducing formation of lithium-containing impurities within the cell,which may be formed via reaction between lithium and an electrolytematerial. In some embodiments, the additive may be an organic ororganometallic compound, a polymer, salts thereof, or combinationsthereof. In some embodiments, the additive may be a neutral species. Insome embodiments, the additive may be a charged species. Additivesdescribed herein may also be soluble with respect to one or morecomponents of the cell (e.g., the electrolyte). In some cases, theadditive may be an electrochemically active species. For example, theadditive may be a lithium salt which may reduce or prevent depletion oflithium and/or the electrolyte, and may also serve as anelectrochemically active lithium salt.

The additive may be present within (e.g., added to) the electrochemicalcell in an amount sufficient to inhibit (e.g., reduce or prevent)formation of impurities and/or depletion of the active materials withinthe cell. “An amount sufficient to inhibit formation of impuritiesand/or depletion of the active materials within the cell,” in thiscontext, means that the additive is present in a large enough amount toaffect (e.g., reduce) formation of impurities and/or the depletion ofthe active materials, relative to an essentially identical cell lackingthe additive. For example, trace amounts of an additive may not besufficient to inhibit depletion of active materials in the cell. Thoseof ordinary skill in the art may determine whether an additive ispresent in an amount sufficient to affect depletion of active materialswithin an electrochemical device. For example, the additive may beincorporated within a component of an electrochemical cell, such as theelectrolyte, and the electrochemical cell may be monitored over a numberof charge/discharge cycles to observe any changes in the amount,thickness, or morphology of the electrodes or electrolyte, or anychanges in cell performance.

Determination of the amount of change in the active materials over anumber of charge/discharge cycles may determine whether or not theadditive is present in an amount sufficient to inhibit formation ofimpurities and/or depletion of the active materials. In some cases, theadditive may be added to the electrochemical cell in an amountsufficient to inhibit formation of impurities and/or depletion of activematerials in the cell by at least 50%, 60%, 70%, 80%, 90%, or, in somecases, by 100%, as compared to an essentially identical cell over anessentially identical set of charge/discharge cycles, absent theadditive.

In some cases, the additive may have the same chemical structure as aproduct of a reaction between lithium of the anode and a solvent withinthe electrolyte, such as an ester, ether, acetal, ketal, or the like.Examples of such solvents include, but are not limited to,1,2-dimethoxyethane and 1,2-dioxolane.

In some cases, the additives described herein may be associated with apolymer. For example, the additives may be combined with a polymermolecule or may be bonded to a polymer molecule. In some cases, theadditive may be a polymer. For example, the additive may have theformula, R′—(O—Li)n, wherein R′ is alkyl or alkoxyalkyl. In someembodiments, an additive is added to an electrochemical cell, whereinthe additive is an electrochemically active species. For example, theadditive can serve as electrolyte salt and can facilitate one or moreprocesses during charge and/or discharge of the cell. In some cases, theadditive may be substantially soluble or miscible with one or morecomponents of the cell. In some cases, the additive may be a salt whichis substantially soluble with respect to the electrolyte. The additivemay serve to reduce or prevent formation of impurities within the celland/or depletion of the active materials, as well as facilitate thecharge-discharge processes within the cell.

Incorporation of additives described herein may allow for the use ofsmaller amounts of lithium and/or electrolyte within an electrochemicalcell, relative to the amounts used in essentially identical cellslacking the additive. As described above, cells lacking the additivesdescribed herein may generate lithium-containing impurities and undergodepletion of active materials (e.g., lithium, electrolyte) duringcharge-discharge cycles of the cell. In some cases, the reaction whichgenerates the lithium-containing impurity may, after a number ofcharge-discharge cycles, stabilize and/or begin to self-inhibit suchthat substantially no additional active material becomes depleted andthe cell may function with the remaining active materials. For cellslacking additives as described herein, this “stabilization” is oftenreached only after a substantial amount of active material has beenconsumed and cell performance has deteriorated. Therefore, in somecases, a relatively large amount of lithium and/or electrolyte has oftenbeen incorporated within cells to accommodate for loss of materialduring consumption of active materials, in order to preserve cellperformance.

Accordingly, incorporation of additives as described herein may reduceand/or prevent depletion of active materials such that the inclusion oflarge amounts of lithium and/or electrolyte within the electrochemicalcell may not be necessary. For example, the additive may be incorporatedinto a cell prior to use of the cell, or in an early stage in thelifetime of the cell (e.g., less than five charge-discharge cycles),such that little or substantially no depletion of active material mayoccur upon charging or discharging of the cell. By reducing and/oreliminating the need to accommodate for active material loss duringcharge-discharge of the cell, relatively small amounts of lithium may beused to fabricate cells and devices as described herein. In someembodiments, devices described herein comprise an electrochemical cellhaving been charged and discharged less than five times in its lifetime,wherein the cell comprises an anode comprising lithium, a cathode, andan electrolyte, wherein the anode comprises no more than five times theamount of lithium which can be ionized during one full discharge cycleof the cell. In some cases, the anode comprises no more than four,three, or two times the amount of lithium which can be ionized duringone full discharge cycle of the cell.

In some embodiments, when an additive is added into the electrolyte thatis added to the electrochemical cell during fabrication, the additivemay first be introduced into the cell as a part of other cell componentsfrom where it can enter the electrolyte. The additive may beincorporated into liquid, gel or solid polymer electrolytes. In someembodiments, the additive may be incorporated in the cathode formulationor into the separator in the fabrication process, as long as it isincluded in a manner such that it will enter the electrolyte insufficient concentrations. Thus, during discharge and charging of thecell, the additive incorporated in the cathode formulation or theseparator may dissolve, at least partially, in the electrolyte.

In some embodiments, an N—O compound can be used as an additive. N—Ocompounds for use as additives include, but are not limited to, familiessuch as inorganic nitrates, organic nitrates, inorganic nitrites,organic nitrites, organic nitro compounds, compounds with negatively,neutral and positively charged NOx groups, and other organic N—Ocompounds. Examples of inorganic nitrates that may be used include, butare not limited to, lithium nitrate, potassium nitrate, cesium nitrate,barium nitrate, and ammonium nitrate. Examples of organic nitrates thatmay be used include, but are not limited to, dialkyl imidazoliumnitrates, and guanidine nitrate. Examples of inorganic nitrites that maybe used include, but are not limited to, lithium nitrite, potassiumnitrite, cesium nitrite, and ammonium nitrite. Examples of organicnitrites that may be used include, but are not limited to, ethylnitrite, propyl nitrite, butyl nitrite, pentyl nitrite, and octylnitrite. Examples of organic nitro compounds that may be used include,but are not limited to, nitromethane, nitropropane, nitrobutanes,nitrobenzene, dinitrobenzene, nitrotoluene, dinitrotoluene,nitropyridine, and dinitropyridine. Examples of other organic N—Ocompounds that may be used include, but are not limited to, pyridineN-oxide, alkylpyridine N-oxides, and tetramethyl piperidine N-oxyl(TEMPO). These and other additives may stabilize lithium/electrolytereactivity, may increase rate of polysulfide dissolution and/or increasesulfur utilization.

When included in electrolyte 106, concentrations of the N—O additive inthe electrolytes may be from about 0.02 m to about 2.0 m (e.g., fromabout 0.1 m to about 1.5 m, or from about 0.2 m to about 1.0 m).Concentrations of the ionic N—O additive when used in embodiments thatdo not include added lithium salts may vary from about 0.2 m to about2.0 m.

In some embodiments, electrochemical cells described herein are adaptedand arranged such that electrolyte compositions are separated todifferent portions of the cell. Such separation can result in isolationof a particular species from a portion of the electrochemical cell, orat least reduction in level of exposure of that portion to the species,for a variety of purposes, including prevention of deposition of certainsolids on or within electrodes of devices of this type.

Separation of electrolyte compositions described herein can be carriedout in a variety of manners. In one set of techniques, a polymer (whichcan be a gel) is positioned at a location in the device where it isdesirable for a particular electrolyte solvent, which has relativelyhigh affinity for the polymer, to reside. In another set of techniques,two different polymers are positioned in the device at particularlocations where two different electrolyte solvents, each having arelatively greater affinity for one of the polymers, are desirablypositioned. Similar arrangements can be constructed using more than twopolymers. Relatively immiscible electrolyte solvents can be used, andpositioned relative to each other, and to other components of thedevice, so as to control exposure of at least one component of thedevice to a particular species, by exploiting the fact that the speciesmay be more highly soluble in one solvent than the other. Techniquesdescribed generally above, or other techniques, or any combination, canbe used toward this general separation methodology.

As described herein, an electrochemical cell may include an anode havinglithium (e.g., lithium metal, a lithium intercalation compound, or alithium alloy) as the active anode species and a cathode having sulfuras the active cathode species. In these and other embodiments, suitableelectrolytes for the lithium batteries can comprise a heterogeneouselectrolyte including a first electrolyte solvent (e.g., dioxolane(DOL)) that partitions towards the anode and is favorable towards theanode (referred to herein as an “anode-side electrolyte solvent”) and asecond electrolyte solvent (e.g., 1,2 dimethoxyethane (DME)) thatpartitions towards the cathode and is favorable towards the cathode (andreferred to herein as an “cathode-side electrolyte solvent”). In someembodiments, the anode-side electrolyte solvent has a relatively lowerreactivity towards lithium metal and may be less soluble to polysulfides(e.g., Li₂Sx, where x>₂) than the cathode-side electrolyte solvent. Thecathode-side electrolyte solvent may have a relatively higher solubilitytowards polysulfides, but may be more reactive towards lithium metal. Byseparating the electrolyte solvents during operation of theelectrochemical cell such that the anode-side electrolyte solvent ispresent disproportionately at the anode and the cathode-side electrolytesolvent is present disproportionately at the cathode, theelectrochemical cell can benefit from desirable characteristics of bothelectrolyte solvents (e.g., relatively low lithium reactivity of theanode-side electrolyte solvent and relatively high polysulfidesolubility of the cathode-side electrolyte solvent). Specifically, anodeconsumption can be decreased, buildup of insoluble polysulfides (i.e.,“slate,” lower-order polysulfides such as Li₂Sx, where x<₃, e.g., Li₂S₂and Li₂S) at the cathode can be decreased, and as a result, theelectrochemical cell may have a longer cycle life. Furthermore, thebatteries described herein may have a high specific energy (e.g.,greater than 400 Wh/kg), improved safety, and/or may be operable at awide range of temperatures (e.g., from −70° C. to +75° C.).Disproportionate presence of one species or solvent, versus another, ata particular location in a cell means that the first species or solventis present, at that location (e.g., at a surface of a cell electrode) inat least a 2:1 molar or weight ratio, or even a 5:1, 10:1, 50:1, or100:1 or greater ratio.

As used herein, a “heterogeneous electrolyte” is an electrolyteincluding at least two different liquid solvents (oftentimes referred toherein as first and second electrolyte solvents, or anode-side andcathode-side electrolyte solvents). The two different liquid solventsmay be miscible or immiscible with one another, although in many aspectsof the invention, electrolyte systems include one or more solvents thatare immiscible (or can be made immiscible within the cell) to the extentthat they will largely separate and at least one can be isolated from atleast one component of the cell. A heterogeneous electrolyte may be inthe form of a liquid, a gel, or a combination thereof.

As certain embodiments described herein involve a heterogeneouselectrolyte having at least two electrolyte solvents that can partitionduring operation of the electrochemical cell, one goal may be to preventor decrease the likelihood of spontaneous solvent mixing, i.e.,generation of an emulsion of two immiscible liquids. As described inmore detail below, this may be achieved in some embodiments by“immobilizing” at least one electrolyte solvent at an electrode (e.g.,an anode) by forming, for example, a polymer gel electrolyte,glassy-state polymer, or a higher viscosity liquid that residesdisproportionately at that electrode.

In some embodiments, an anode includes a polymer layer adjacent amultilayered structure of the anode (e.g., positioned as an outerlayer). The polymer layer can, in some instances, be in the form of apolymer gel or a glassy-state polymer. The polymer layer may have anaffinity to one electrolyte solvent of a heterogeneous electrolyte suchthat during operation of the electrochemical cell, a first electrolytesolvent resides disproportionately at the anode, while a secondelectrolyte solvent is substantially excluded from the polymer layer andis present disproportionately at the cathode. For example, a firstelectrolyte solvent may reside predominately at a polymer layer adjacentthe anode. Because the first electrolyte solvent is present closer tothe anode, it is generally chosen to have one or more characteristicssuch as low reactivity to lithium (e.g., enable high lithiumcycle-ability), reasonable lithium ion conductivity, and relativelylower polysulfide solubility than the second electrolyte solvent (sincepolysulfides can react with lithium). The second electrolyte solvent maybe present disproportionately at the cathode and, for example, mayreside substantially in a separator, a polymer layer adjacent thecathode, and/or in a base electrode material layer of the cathode (e.g.,cathode active material layer). For example, a second electrolytesolvent may reside predominately at a polymer layer adjacent thecathode, predominately in the base electrode material layer, or incombinations thereof. In some instances, the second electrolyte solventis essentially free of contact with the anode. The second electrolytesolvent may have characteristics that favor better cathode performancesuch as high polysulfide solubility, high rate capability, high sulfurutilization, and high lithium ion conductivity, and may have a wideliquid state temperature range. In some cases, the second electrolytesolvent has a higher reactivity to lithium than the first electrolytesolvent. It may be desirable, therefore, to cause the second electrolytesolvent to be present at the cathode (i.e., away from the anode) duringoperation of the electrochemical cell, thereby effectively reducing itsconcentration, and reactivity, at the anode.

As described above, the first electrolyte solvent of a heterogeneouselectrolyte may be present disproportionately at the anode by residingin a polymer layer positioned adjacent a multi-layered structure.Accordingly, the material composition of the polymer layer may be chosensuch that the polymer has a relatively higher affinity to (highsolubility in) the first electrolyte solvent compared to the secondelectrolyte solvent. For instance, in some embodiments, the polymerlayer is prepared in the form of a gel by mixing a monomer, a firstelectrolyte solvent, and, optionally, other components (e.g., acrosslinking agent, lithium salts, etc.) and disposing this mixture onthe anode. The monomer can be polymerized by various methods (e.g.,using a radical initiator, ultra violet radiation, an electron beam, orcatalyst (e.g., an acid, base, or transition metal catalyst)) to form agel electrolyte. Polymerization may take place either before or afterdisposing the mixture on the anode. After assembling the othercomponents of the cell, the cell can be filled with the secondelectrolyte solvent. The second electrolyte solvent may be excluded fromthe polymer layer (e.g., due to the high affinity of the polymer withthe first electrolyte solvent already present in the polymer layerand/or due to immiscibility between the first and second electrolytesolvents). In some instances, the second electrolyte solvent may fillthe spaces (e.g., pores) within the separator and/or the cathode. Insome embodiments, the cathode can be dried prior to assembly of theelectrochemical cell to facilitate this process. Additionally and/oralternatively, the cathode (e.g., base electrode material layer of thecathode) may include a polymer that has a high affinity for the secondelectrolyte solvent. The polymer in the base electrode material layermay be in the form of particles. In some cases, the second electrolytecan reside at least partially in a polymer layer positioned adjacent thecathode.

In another embodiment, a polymer layer is formed at the anode and isdried prior to assembly of the cell. The cell can then be filled with aheterogeneous electrolyte including the first and second electrolytesolvents. If the polymer layer is chosen such that it has a higheraffinity towards the first electrolyte solvent (and/or the separatorand/or cathode may have a higher affinity towards the second electrolytesolvent), at least portions of the first and second electrolyte solventscan partition once they are introduced into the cell. In yet anotherembodiment, partitioning of the first and second electrolyte solventscan take place after commencement of first discharge of the cell. Forexample, as heat is produced while operating the battery, the affinitybetween the polymer layer and the first electrolyte solvent can increase(and/or the affinity between the separator and/or cathode and the secondelectrolyte solvent can increase). Thus, a greater degree ofpartitioning of the electrolyte solvents can occur during operation ofthe cell. Additionally, at lower temperatures, the effect may beirreversible such that the first electrolyte solvent is trapped withinthe polymer layer, and the second electrolyte solvent is trapped withinthe pores of the separator and/or cathode.

In some cases, the components of the electrochemical cell (e.g., thepolymer layer) may be pretreated (e.g., with heat) prior to use toaffect the desired degree of polymer/electrolyte solvent interaction.Other methods of partitioning the electrolyte solvents are alsopossible.

In another embodiment, the polymer layer is deposited at the anode andthe anode (including the polymer layer) is exposed to a firstelectrolyte solvent. This exposure can cause the first electrolytesolvent to be absorbed in the polymer. The cell can be formed bypositioning a cathode adjacent the anode such that the polymer layer ispositioned between the anode and cathode. The cathode can then beexposed to a second electrolyte solvent, e.g., such that at least aportion of the second electrolyte solvent is absorbed in the cathode. Inother embodiments, the cathode can be exposed to the second electrolytesolvent prior to assembly of the anode and cathode. Optionally, thecathode may include a polymer layer that preferentially absorbs thesecond electrolyte solvent more than the first electrolyte solvent. Insome embodiments, e.g., by choosing appropriate polymer(s) and/ormaterials used to form the anode and/or cathode, at least portions ofthe first and second electrolyte solvents can be separated within thecell. For instance, a higher proportion of the first electrolyte solventmay reside at the anode and a higher proportion of the secondelectrolyte solvent may reside at the cathode.

In yet another embodiment, an electrochemical cell does not include apolymer layer specifically used for partitioning at the anode or thecathode. A separator may include a different composition near the anodeside compared to the cathode side of the separator, the anode sidehaving a higher affinity for the first solvent and the cathode sidehaving a higher affinity for the second solvent. Additionally and/oralternatively, the second electrolyte solvent may be presentdisproportionately at the cathode by, for example, fabricating thecathode such that it contains a component that has a high affinity forthe second electrolyte solvent.

In some of the embodiments described herein, an electrochemical cell maybe filled with a heterogeneous electrolyte including first and secondelectrolyte solvents and partitioning of the electrolyte solvents canoccur after commencement of first discharge of the cell, e.g., due tothe differential solubility of the polysulfides in the electrolytesolvents. For example, as more polysulfides are generated duringoperation of the cell, the dissolution of the polysulfides in the morefavorable second electrolyte solvent can cause it to become immisciblewith the first. Thus, in some embodiments, the first and secondelectrolyte solvents may be miscible before, but immiscible after,commencement of first discharge of the battery. The second electrolytesolvent containing the dissolved polysulfides may be presentdisproportionately at the cathode by, for example, embodiments describedherein such as having a polymer layer at the anode that preferentiallyassociates with the first electrolyte solvent, and/or a polymer layer atthe cathode that preferentially associates with the second electrolytesolvent. In other embodiments, the first and second electrolyte solventsare miscible before commencement of first discharge of the cell, but theelectrolyte solvents become immiscible due to heating of the electrolytesolvents during operation of the cell. In yet other embodiments, thefirst and second electrolyte solvents are immiscible before and aftercommencement of first discharge of the cell. For instance, the first andsecond electrolyte solvents may be inherently immiscible at roomtemperature, as well as during operation of the battery. Advantageously,in some embodiments, two immiscible liquid electrolyte solvents, onepresent disproportionately and the anode and the other presentdisproportionately and the cathode, do not cause additional mechanicalstress to the battery as a solid membrane may, during electrode volumechanges that occur during cell cycling.

As described herein, in some embodiments a polymer that has an affinityfor an electrolyte solvent can be dispersed within the cathode (e.g., ina base electrode material layer). For instance, the cathode activematerial layer may include a polymeric material in powder formincorporated therein. In some cases, the polymeric material is aninsoluble component in the cathode layer. For example, the polymericmaterial may be insoluble in the solvent used to dissolve the cathodeactive material. The polymer can be obtained, or modified, to have asuitable particle size and dispersed throughout the cathode byincorporation in the cathode slurry. One advantage of incorporating aninsoluble polymer with the cathode active material layer is that thepolymer can remain as discrete particles that do not coat, adsorb,and/or block the active carbon sites. In other cases, however, thepolymeric material can be dissolved, or partially dissolved, as thecathode binder in the cathode layer.

In certain embodiments including one or more polymers dispersed within alayer (e.g., insoluble polymeric particles dispersed in a cathode), thepolymers can have any suitable particle size. The average diameter ofthe polymer particles may be, for example, less than or equal to 100microns, less than or equal to 70 microns, less than or equal to 50microns, less than or equal to 30 microns, less than or equal to 15microns, less than or equal to 10 microns, or less than or equal to 5microns. Of course, a range of polymer particle sizes may be used. Forexample, in one embodiment, the polymer particles may have a size ofd10=5, d50=12, and d97=55 microns, meaning 10% of the particles werebelow 5 microns, 50% of the particles below 12 microns, and only 3% ofthe particles measured above 55 microns.

Suitable polymer materials for partitioning electrolyte solvents mayinclude the polymers described herein, such as those mentioned aboveregarding suitable polymeric materials for polymer layers (e.g., as partof a multi-layer protective structure). In some embodiments, a singlepolymer layer is in contact with an anode or cathode of anelectrochemical cell; however, in other embodiments, more than onepolymer layer can be associated with an anode or cathode. For instance,a polymer layer in contact with an anode (or cathode) may be formed ofmore than one polymer layer coated in sequence. The sequence of polymersmay include, for example, a first polymer and a second polymer, thefirst and second polymers being the same or different. Additionalpolymers, e.g., fourth, fifth, or sixth polymer layers, can also beused. Each of the polymer layers may optionally include one or morefillers or other components (e.g., crosslinking agents, lithium salts,etc.).

The thickness of a polymer layer may vary, e.g., over a range from about0.1 microns to about 100 microns. The thickness of the polymer layer maydepend on, for example, whether it is positioned adjacent the anode orcathode, whether a separator is also present in the battery, and/or thenumber of polymer layers in the cell. For instance, the thickness of thepolymer layer may be between 0.1-1 microns thick, between 1-5 micronsthick, between 5-10 microns thick, between 10-30 microns thick, orbetween 30-50 microns thick, between 50-70 microns thick, or between50-100 microns thick. In some embodiments, the thickness of a polymerlayer may be no greater than, e.g., 50 microns thick, no greater than 25microns thick, no greater than 10 microns thick, no greater than 5microns thick, no greater than 2.5 microns thick, no greater than 1micron thick, no greater than 0.5 microns thick, or no greater than 0.1microns thick.

As set forth above, in accordance with further exemplary embodiments ofthe invention, electrolyte 106 includes a nitrogen-containing groupattached to an insoluble cation, monomer, oligomer, or polymer to forman insoluble nitrogen-containing material in the electrolyte. Compounds,such as salts of K, Mg, Ca, Sr, Al, aromatic hydrocarbons, or ethers asbutyl ether may additionally or alternatively be added to theelectrolyte to reduce the solubility of nitrogen-containing compounds,such as inorganic nitrate, organic nitrates, inorganic nitrites, organicnitrites, organic nitro compounds, and the like, such that any of thenitrogen-containing compounds described herein become substantiallyinsoluble nitrogen-containing compounds as defined herein.

In accordance with various exemplary embodiments of the invention,electrolyte 106 includes about 30% to about 90%, or about 50% to about85%, or about 60% to about 80% solvents, about 0.1% to about 10%, orabout 0.5% to about 7.5%, or about 1% to about 5% N—O additive, andabout 1% to about 20%, or about 1% to about 10%, or about 1% to about 5%substantially insoluble nitrogen-containing material, and up to about20%, or about 4% to about 20%, or about 6% to about 16%, or about 8% toabout 12% LiTFSI.

Referring again to FIG. 1, in accordance with various embodiments of theinvention, electrochemical cell 100 includes separator 108 interposedbetween cathode 102 and anode 104. The separator may be a solidnon-conductive or insulative material which separates or insulates theanode and the cathode from each other preventing short circuiting. Thepores of the separator may be partially or substantially filled withelectrolyte.

Separators may be supplied as porous free standing films which areinterleaved with the anodes and the cathodes during the fabrication ofcells. Alternatively, the porous separator layer may be applied directlyto the surface of one of the electrodes.

A variety of separator materials are known in the art. Examples ofsuitable solid porous separator materials include, but are not limitedto, polyolefins, such as, for example, polyethylenes and polypropylenes,glass fiber filter papers, and ceramic materials. Further examples ofseparators and separator materials suitable for use in this inventionare those comprising a microporous xerogel layer, for example, amicroporous pseudo-boehmite layer, which may be provided either as afree-standing film or by a direct coating application on one of theelectrodes. Solid electrolytes and gel electrolytes may also function asa separator in addition to their electrolyte function and which permitsthe transport of ions between the anode and the cathode.

In accordance with various embodiments of the invention, separator 108may include one or more nitrogen-containing materials, such as one ormore monomers, oligomers and/or polymers selected from the groupconsisting of: polyethylene imine, polyphosphazene, polyvinylpyrolidone,polyacrylamide, polyaniline, polyelectrolytes (e.g., having a nitroaliphatic portion as a functional group), and amine groups, such aspolyacrylamide, polyallylaminde and polydiallyldimethylammoniumchloride, polyimides, polybenzimidazole, polyamides, and the like.

The composition of the nitrogen-containing material in separator 108 maybe up to 100% or about 30% to about 60%. The separator may be up toabout 20%, or about 4% to about 6% of the electrochemical cell weight.

An electrochemical cell may include any suitable current collector 112,114. A current collector is useful in efficiently collecting theelectrical current generated throughout an electrode and in providing anefficient surface for attachment of the electrical contacts leading tothe external circuit. A wide range of current collectors are known inthe art. Suitable current collectors may include, for example, metalfoils (e.g., aluminum foil), polymer films, metallized polymer films(e.g., aluminized plastic films, such as aluminized polyester film),electrically conductive polymer films, polymer films having anelectrically conductive coating, electrically conductive polymer filmshaving an electrically conductive metal coating, and polymer filmshaving conductive particles dispersed therein.

In some embodiments, the current collector includes one or moreconductive metals such as aluminum, copper, chromium, stainless steeland nickel or an alloy or alloys of such metals. Other currentcollectors may include, for example, expanded metals, metal mesh, metalgrids, expanded metal grids, metal wool, woven carbon fabric, wovencarbon mesh, non-woven carbon mesh, or carbon felt. Furthermore, acurrent collector may be electrochemically inactive or may comprise anelectroactive material. For example, a current collector may include amaterial that is used as an electroactive material layer (e.g., as ananode or a cathode such as those described herein).

A current collector may be positioned on a surface by any suitablemethod such as lamination, sputtering, or vapor deposition. In somecases, a current collector is provided as a commercially available sheetthat is laminated with one or more electrochemical cell components. Inother cases, a current collector is formed during fabrication of theelectrode by depositing a conductive material on a suitable surface.Side or edge current collectors may also be incorporated intoelectrochemical cells described herein.

A current collector may have any suitable thickness. For instance, thethickness of a current collector may be, for example, between 0.1 and0.5 microns thick, between 0.1 and 0.3 microns thick, between 0.1 and 2microns thick, between 1-5 microns thick, between 5-10 microns thick,between 5-20 microns thick, or between 10-50 microns thick. In certainembodiments, the thickness of a current collector is, e.g., about 20microns or less, about 12 microns or less, about 10 microns or less,about 7 microns or less, about 5 microns or less, about 3 microns orless, about 1 micron or less, about 0.5 micron or less, or about 0.3micron or less. In some embodiments, the use of a release layer duringfabrication of an electrode can allow the formation or use of a verythin current collector, which can reduce the overall weight of the cell,thereby increasing the cell's energy density.

As previously stated, electrochemical cells in accordance with variousembodiments of the invention may include one or more nitrogen-containingcompounds in one or more components of a cell. For example, the cell mayinclude a cathode, an anode, a separator between the anode and cathode,a non-aqueous electrolyte, and a nitrogen-containing material in one ormore of the group consisting of the anode, the cathode, and theseparator. Alternatively, the cell may include a cathode, an anode,optionally a separator between the anode and cathode, a non-aqueouselectrolyte, and a nitrogen-containing material in one or more of thegroup consisting of the anode, the cathode, the separator, and theelectrolyte, wherein, the nitrogen-containing compound is substantiallyinsoluble in the electrolyte, and may be selected from the groupconsisting of include one or more monomers, oligomers and/or polymersselected from the group consisting of: polyethylene imine,polyphosphazene, polyvinylpyrolidone, polyacrylamide, polyaniline,polyelectrolytes (e.g., having a nitro aliphatic portion as a functionalgroup), and amine groups, such as polyacrylamide, polyallylaminde andpolydiallyldimethylammonium chloride, polyimides, polybenzimidazole, andpolyamides. The nitrogen-containing materials may be substantiallyinsoluble in the electrolyte, attached to a moiety that is substantiallyinsoluble in the electrolyte, and/on form part of the cathode, anode,separator, or portion(s) thereof, such that the cell portion includes afunctional group including nitrogen, which may be substantiallyinsoluble in the electrolyte. The exemplary cells may additionallyinclude N—O additives in the electrolyte. By way of examples, the anode;the cathode; the separator; the electrolyte; the anode and cathode; theseparator and one or both of the anode and cathode; the electrolyte andone or both of the anode and cathode; the anode, the cathode and theseparator; the anode, the cathode and the electrolyte, the anode, thecathode, the electrolyte, and the separator may include thenitrogen-containing materials as described herein.

Batteries, such as battery 400, in accordance with various exemplaryembodiments of the invention, include one or more cells 408 as describedherein, current collectors (e.g., collectors 112, 114), leads orterminals (e.g., a positive lead 404 and a negative lead 406)electrically coupled to the collectors, and a casing or housing 402,which encapsulates at least a portion of the cell.

The present invention has been described above with reference to anumber of exemplary embodiments and examples. It should be appreciatedthat the particular embodiments shown and described herein areillustrative of the preferred embodiments of the invention and its bestmode, and are not intended to limit the scope of the invention as setforth in the claims. It will be recognized that changes andmodifications may be made to the embodiments described herein withoutdeparting from the scope of the present invention. These and otherchanges or modifications are intended to be included within the scope ofthe present invention, as expressed in the following claims and thelegal equivalents thereof.

The invention claimed is:
 1. An electrochemical cell, comprising: acathode; an anode comprising lithium; a porous separator between theanode and cathode; and a non-aqueous electrolyte comprising about 50 wt% to about 85 wt % of one or more non-aqueous solvents, about 0.2 m(moles/kg of solvent) to about 2.0 m of one or more lithium salts, andabout 1 wt % to about 5 wt % of a substantially insolublenitrogen-containing material, wherein the solubility of thesubstantially insoluble nitrogen-containing material in the electrolyteis less than 1%, wherein at least a portion of the non-aqueouselectrolyte is within pores of the separator, and wherein thesubstantially insoluble nitrogen-containing material comprises one ormore of a nitro compound, polydiallyldimethylammonium chloride, anitrate or nitrite in combination with a salt, aromatic hydrocarbon, orether added to the electrolyte to make the nitrate or nitrite insolublein the electrolyte, a compound including an N—O or amine functionalgroup attached to a carbon chain comprising about 8 to about 25 carbonatoms configured to form micelle structures comprising the N—O or aminefunctional groups, polyethylene imine, polyvinylpyrolidone,polyacrylamide, polyaniline, and polybenzimidazole.
 2. Theelectrochemical cell of claim 1, further comprising about 0.5 wt % toabout 7.5 wt % of an additive comprising an N—O compound.
 3. Theelectrochemical cell of claim 1, wherein the substantially insolublenitrogen containing material comprises a nitro compound,polydiallyldimethylammonium chloride, polyamide or a nitrate or nitritein combination with a salt, aromatic hydrocarbon, or ether added to theelectrolyte to make the nitrate or nitrite insoluble in the electrolyte,or a compound including an N—O or amine functional group attached to acarbon chain comprising about 8 to about 25 carbon atoms configured toform micelle structures comprising the N—O or amine functional groups.4. A battery comprising: a housing; a positive lead; a negative lead;and one or more electrochemical cells as defined in claim
 1. 5. Anelectrochemical cell, comprising: a cathode comprising an electroactivematerial; an anode comprising lithium; a separator between the anode andcathode; and a non-aqueous electrolyte comprising about 60 wt % to about80 wt % of one or more non-aqueous solvents, about 0.2 m (moles/kg ofsolvent) to about 2.0 m of one or more lithium salts, about 1 wt % toabout 10 wt % of a substantially insoluble nitrogen-containing material,wherein the solubility of the substantially insolublenitrogen-containing material in the electrolyte is less than 1%, whereinthe separator comprises pores, wherein at least a portion of thenon-aqueous electrolyte is within the pores, and wherein thesubstantially insoluble nitrogen-containing material comprises one ormore of a nitro compound, polydiallyldimethylammonium chloride, anitrate or nitrite in combination with a salt, aromatic hydrocarbon, orether added to the electrolyte to make the nitrate or nitrite insolublein the electrolyte, a compound including an N—O or amine functionalgroup attached to a carbon chain comprising about 8 to about 25 carbonatoms configured to form micelle structures comprising the N—O or aminefunctional group, polyethylene imine, polyvinylpyrolidone,polyacrylamide, polyaniline, and polybenzimidazole.
 6. Theelectrochemical cell of claim 5, wherein the solubility of thesubstantially insoluble nitrogen-containing material in the non-aqueouselectrolyte is less than 0.5 percent.
 7. The electrochemical cell ofclaim 5, wherein the substantially insoluble nitrogen-containingmaterial comprises the compound including the N—O or amine functionalgroup attached to the carbon chain comprising about 8 to about 25 carbonatoms configured to form micelle structures comprising the N—O or aminefunctional group.
 8. The electrochemical cell of claim 5, wherein thesubstantially insoluble nitrogen-containing material comprises acompound selected from the group consisting of polynitrostyrene,nitrocellulose, and octyl nitrate.
 9. The electrochemical cell of claim5, wherein the substantially insoluble nitrogen-containing materialcomprises polyethylene imine.
 10. The electrochemical cell of claim 5,wherein the substantially insoluble nitrogen-containing materialcomprises the nitrate or nitrite in combination with a salt, aromatichydrocarbon, or ether added to the electrolyte to make the nitrate ornitrite insoluble in the electrolyte.
 11. The electrochemical cell ofclaim 5, wherein the substantially insoluble nitrogen-containingmaterial comprises the nitro compound.
 12. The electrochemical cell ofclaim 5, wherein the substantially insoluble nitrogen-containingmaterial comprises a nitrogen group attached to an insoluble materialselected from the group consisting of a cation, a monomer, an oligomer,and a polymer.
 13. The electrochemical cell of claim 5, wherein thecathode includes the substantially insoluble nitrogen-containingmaterial.
 14. The electrochemical cell of claim 5, wherein the cathodecomprises a binder comprising the substantially insolublenitrogen-containing material.
 15. The electrochemical cell of claim 5,wherein the anode includes the substantially insolublenitrogen-containing material.
 16. The electrochemical cell of claim 5,wherein the non-aqueous electrolyte comprises a compound selected fromthe group consisting of a potassium salt, a magnesium salt, a calciumsalt, a strontium salt, an aluminum salt, an aromatic hydrocarbon, andan ether.
 17. The electrochemical cell of claim 5, wherein the one ormore lithium salts comprise LiTFSI, and wherein the electrolytecomprises about 60 wt % to about 80 wt % of the one or more non-aqueoussolvents, about 1 wt % to about 5 wt % of an N—O additive, about 1 wt %to about 5 wt % of the substantially insoluble nitrogen-containingmaterial, and up to about 20 wt % LiTFSI.
 18. The electrochemical cellof claim 5, further comprising about 1 wt % to about 5 wt % of anadditive comprising an N—O compound.
 19. The electrochemical cell ofclaim 3, wherein the N—O compound is selected from the group consistingof inorganic nitrates, organic nitrates, inorganic nitrites, organicnitrites, organic nitro compounds, and compounds with one or more ofnegatively, neutral and positively charged nitrogen oxide groups.
 20. Abattery comprising: a housing; a positive lead; a negative lead; and oneor more electrochemical cells as defined in claim 5.